In power generation systems using gas engines, in order to stably generate electricity, a combustion abnormality such as knocking needs to be found at an early stage to be prevented.
For example, Patent Literature 1 discloses a control device in which, when it is determined that knocking has occurred in any of the air cylinders in a gas engine on the basis of a value detected using a knock sensor, a supply amount and pressure of a gas with respect to all of the air cylinders are reduced so that a load is lowered or an ignition timing is delayed (a timing retard) and thus the occurrence of knocking is minimized.